This document discusses a hybrid cloud approach for authorized data deduplication. It proposes a system where a private cloud acts as a proxy between data owners/users and a public cloud storage provider. The private cloud manages differential privilege keys and allows users to securely check for duplicate files based on their privileges. The system aims to protect data confidentiality while supporting an authorized form of deduplication across users with different access levels.

1. A Hybrid Cloud Approach for Secure
Authorized Deduplication
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2. DOTNET
WHY ? WHAT? WHERE?
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3. Design Features of DOT NET Framework
 Interoperability.
 Common Language Runtime engine (CLR)
 Language independence.
 Base Class Library.
 Simplified deployment.
 Security.
 Portability.
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5.  Data deduplication is one of important data compression techniques
for eliminating duplicate copies of repeating data, and has been
widely used in cloud storage to reduce the amount of storage space
and save bandwidth. To protect the confidentiality of sensitive data
while supporting deduplication, the convergent encryption technique
has been proposed to encrypt the data before outsourcing. To better
protect data security, this paper makes the first attempt to formally
address the problem of authorized data deduplication. Different
from traditional deduplication systems, the differential privileges of
users are further considered in duplicate check besides the data
itself. We also present several new deduplication constructions
supporting authorized duplicate check in a hybrid cloud
architecture. Security analysis demonstrates that our scheme is
secure in terms of the definitions specified in the proposed security
model.
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6.  Data deduplication systems, the private cloud
is involved as a proxy to allow data
owner/users to securely perform duplicate
check with differential privileges.
 Such architecture is practical and has
attracted much attention from researchers.
 The data owners only outsource their data
storage by utilizing public cloud while the
data operation is managed in private cloud.
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7.  In this paper, we enhance our system in security.
Specifically, we present an advanced scheme to
support stronger security by encrypting the file
with differential privilege keys. In this way, the
users without corresponding privileges cannot
perform the duplicate check. Furthermore, such
unauthorized users cannot decrypt the cipher
text even collude with the S-CSP. Security
analysis demonstrates that our system is secure
in terms of the definitions specified in the
proposed security model.
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8.  Cloud Service Provider
 Data Users Module
 Private Cloud Module
 Secure Deduplication System
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9. Cloud Service Provider
 In this module, we develop Cloud Service
Provider module. This is an entity that provides a
data storage service in public cloud. The S-CSP
provides the data outsourcing service and stores
data on behalf of the users.To reduce the storage
cost, the S-CSP eliminates the storage of
redundant data via deduplication and keeps only
unique data. In this paper, we assume that S-CSP
is always online and has abundant storage
capacity and computation power.
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10.  A user is an entity that wants to outsource data
storage to the S-CSP and access the data later. In
a storage system supporting deduplication, the
user only uploads unique data but does not
upload any duplicate data to save the upload
bandwidth, which may be owned by the same
user or different users. In the authorized
deduplication system, each user is issued a set of
privileges in the setup of the system. Each file is
protected with the convergent encryption key and
privilege keys to realize the authorized
deduplication with differential privileges.
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11.  We consider several types of privacy we need protect,
that is, i) unforgeability of duplicate-check token:
There are two types of adversaries, that is, external
adversary and internal adversary.
 As shown below, the external adversary can be
viewed as an internal adversary without any privilege.
 If a user has privilege p, it requires that the adversary
cannot forge and output a valid duplicate token with
any other privilege p′ on any file F, where p does not
match p′. Furthermore, it also requires that if the
adversary does not make a request of token with its
own privilege from private cloud server, it cannot
forge and output a valid duplicate token with p on
any F that has been queried.
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12.  Compared with the traditional deduplication architecture
in cloud computing, this is a new entity introduced for
facilitating user’s secure usage of cloud service.
 Specifically, since the computing resources at data
user/owner side are restricted and the public cloud is not
fully trusted in practice, private cloud is able to provide
data user/owner with an execution environment and
infrastructure working as an interface between user and
the public cloud.
 The private keys for the privileges are managed by the
private cloud, who answers the file token requests from
the users. The interface offered by the private cloud allows
user to submit files and queries to be securely stored and
computed respectively.
 Secure Deduplication System
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